Re: [PATCH V4 3/3] perf tool: Add sort key symoff for perf diff

From: Namhyung Kim
Date: Thu Nov 20 2014 - 01:18:50 EST

On Tue, 18 Nov 2014 18:13:19 -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Nov 18, 2014 at 11:38:20AM -0500, kan.liang@xxxxxxxxx escreveu:
>> From: Kan Liang <kan.liang@xxxxxxxxx>
>> Sometime, especially debugging scaling issue, the function level diff
>> may be high granularity. The user may want to do deeper diff analysis
>> for some cache or lock issue. The "symoff" key can let the user sort
>> differential profile by ips. This feature should only work when the
>> comes from same binary.
> So, to avoid having people scratching heads, and since we have the
> build-id for both files, hence for both binaries being
> compared, can we check the build ids and either refuse to do the diff or
> print a big warning about different binaries being compared?

Why do you think so? I think it's fine to use symoff for different
binaries for same reason as the symbol sort key. Even if some functions
were changed, other DSOs and/or functions still have same offset and
thus have meaningful diff result IMHO.

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